Aiming to improve the utilization of bromine resources in bittern, the solubilities of the ternary NaCl−NaBr−CH 3 OH−H 2 O mixed solvent system at 298 and 323 K were measured by the method of isothermal dissolution equilibrium, and the corresponding phase diagrams were constructed. The results show that the phase diagrams at the two temperatures are similar, and both have only one univariant curve and one crystallization region corresponding to a solid solution Na(Cl, Br) without invariant points. Based on the extended Pitzer model, Pitzer parameters were calculated, and the activity product of the solid solution was regressed into a polynomial of Br − mole fraction in the solid solution. The solubilities of the ternary NaCl−NaBr− CH 3 OH−H 2 O mixed solvent system at 298 K were calculated. The computed results are in accordance with the experimental values.
Background: An improved hydrothermal-calcination method was used to convert desulphurization gypsum containing organic matter (OM-gypsum) to insoluble anhydrite (II-CaSO 4 ) whiskers, where OM-gypsum was directly transformed to soluble anhydrite (γ-CaSO 4 ) whiskers via the hydrothermal method followed by calcination. The synthesized II-CaSO 4 whiskers were applied for the removal of lead ion (Pb(II)) and zinc ion (Zn(II)).Results: The synthesized II-CaSO 4 whiskers possessed a smooth surface, large aspect ratio, and high whiteness of above 90%. The mother liquor after synthesis could be recycled. The synthesized II-CaSO 4 whiskers exhibited maximum adsorption capacities of 641.03 mg/g and 14.00 mg/g for Pb(II) and Zn(II), respectively, under optimal adsorption conditions. The pseudo-second-order model and Langmuir isotherm model were appropriate for describing the adsorption process of II-CaSO 4 whiskers. Compared with II-CaSO 4 whiskers calcined from hemihydrate gypsum and the short and columnar II-CaSO 4 crystals, the synthesized II-CaSO 4 whiskers in this work possessed a superior adsorption performance. Conclusion:The improved hydrothermal-calcination process could completely remove the organic matter from OM-gypsum, and the direct formation of γ-CaSO 4 intermediate helped avoid the lattice collapse caused by the removal of water molecules during calcination. The excellent adsorption performance of the synthesized II-CaSO 4 whiskers in this work could be attributed to their large negatively charged surface areas, which were formed by the large aspect ratio and excellent stability. This work provides a practical method for the comprehensive utilization of chemical gypsum containing organic impurities.
Zeolite W with the spindle morphology has been rapidly synthesized from alkali fusion activated K-feldspar via gel-like-solid phase method after supplementing a small amount of silica-aluminum xerogel. The effects of n(H 2 O)/n (SiO 2 ), m (activation product)/m (xerogel), and crystallization time on the synthesis of zeolite W were investigated. The optimal synthesis conditions were m (activation product)/m (xerogel) of 3.92, n(H 2 O)/n (SiO 2 ) of 25.8, and crystallization time of 12 h. The synthesized zeolite W was used to extract K + ion from the simulated seawater. The synthesized zeolite W with the fluffier spindle morphology exhibited a higher K + extraction capacity. The maximum exchange capacity of zeolite W for K + ion reached 49.57 mgÁg À1 . The zeolite W synthesized by the gel-like-solid phase method possessed a superior K + extraction capacity than that synthesized by the hydrothermal method when K-feldspar was used as the raw material and an approximate K + extraction capacity with that synthesized from chemical reagents. In addition, the recycling process of the mother liquor was designed. This work provides an effective way for the zeolite W synthesis and the resource utilization of K-feldspar with advantages of high raw material utilization, low water content in the synthesis system, short crystallization time, and recyclable mother liquor after synthesis of zeolite W.
The comprehensive utilization of coal gangue (CG) is restricted by color elements in CG including C and Fe x O y . The magnetic separation and hydrothermal acid leaching are combined to pretreat the solid waste CG to synthesize zeolite A with high whiteness. Firstly, Fe 2 O 3 component in CG is in situ reduced by C to magnetite in the process of high-temperature calcination for decarburization followed by physical magnetic separation. Secondly, the residual Fe impurity in CG is further removed by hydrothermal acid leaching. The effects of calcination temperature, calcination time, acid leaching temperature, acid concentration, and liquid to solid ratio on Fe removal rate (R Fe2O3 ) and the whiteness of the synthesized zeolite A are investigated. The influence of Fe impurities on the Ca 2+ ion exchange capacity (E) of the zeolite A synthesized from CG is clarified. R Fe2O3 could reach the value of 88.53%. The synthesized zeolite A exhibits a typical cubic morphology with rounded edges, the high whiteness of 95.46%, and the satisfactory E with the value of 296.02 mgCaCO 3 Ág À1 , both of which meet the requirements of national standard. This work suggests that this pretreatment method for CG would have broad prospects in the efficient resource utilization of CG.
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